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In order to use WireGuard, first of all, you will need to acquire private and public keys.
You could do so, by following instruction given in a OpenWRT forum.
Once, you have keys, navigate to Services - VPN - Wireguard (if you do not see WireGuard in a VPN list, please install this package using Package manager), enable service, add new peer with given VPN provider information and save configuration.
Once this done, you could check if tunnel is alive using wg command in SSH/CLI.
More information about WireGuard configuration in Teltonika devices could be found in our wiki.
Hope it helps.